Technical Field
The present disclosure is related to an unlicensed spectrum communication scheme applied in the wireless communication system, and more particular to a method and device for communication on an unlicensed spectrum based on Long Term Evolution (LTE).
Related Art
In the LTE system, the base station may transmit a downlink control indicator (DCI) to trigger an aperiodic sounding reference signal (A-SRS). The DCI format {0, 1A, 2B, 2C, 2D, 4} supports and triggers the A-SRS. For the UE, if a first DCI triggering the A-SRS is received, the SRS is transmitted on an uplink physical resource of a serving cell scheduled by the first DCI.
The serving cell includes a downlink carrier (or sub frame) and an uplink carrier (or sub frame). A cell index of the serving cell, a frequency band (or sub frame) of the downlink carrier and a frequency band (or sub frame) of the uplink carrier are semi-statically configured by a higher layer signaling.
In the traditional LTE system of the 3rd Generation Partner Project (3GPP), the data transmission only occurs on the licensed spectrum; however, with the sharp increase on the communication amount, especially in some urban areas, the licensed spectrum may be difficult to meet the demand of the communication amount. A new research topic is discussed in the 62th 3GPP RAN plenary, i.e. the comprehensive research of the unlicensed spectrum (RP-132085). The main purpose is to research the non-standalone deployment of LTE on the unlicensed spectrum, wherein the so-called non-standalone means that the communication on the unlicensed spectrum is required to be associated with the serving cell on the licensed spectrum. An intuitive approach is to reuse the carrier aggregation (CA) in the existing system as much as possible, i.e. the serving cell deployed on the licensed spectrum serves as the primary component carrier (PCC), and the serving cell deployed on the unlicensed spectrum serves as the secondary component carrier (SCC). For the unlicensed spectrum, considering the interference level thereof may not be controlled/predicted, such that the UE may be configured with more carriers, and (in a given sub frame) a part of carriers is selected from the selectable carriers to be used to transmit the data through a dynamical frequency selection (DFS) manner at the same time.
In the communication of the unlicensed spectrum, a triggering mechanism of the traditional A-SRS may encounter the following problem.
The base station may not be dynamically triggered to transmit SRS on the non-scheduled serving cell (A-SRS is transmitted on the serving cell scheduled by the scheduled DCI thereof).
For the above problems, the present disclosure discloses a method and device for SRS scheduling on an unlicensed spectrum.